检索结果-南通市图书馆

Ray Structure of the Coronal Streamer Belt and Its Manifestation as Sharp Large Peaks of Solar Wind Plasma Density at the Earth's Orbit

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

空间科学学报 2005年第5期25卷 321-328页

作者： M. V. Eselevich V. G. Eselevich z. q. z.ng Institute of Solar-Terrestrial Physics Siberian Branch Russian Academy of Sciences Irkutsk 664033 Russia Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080 China

The white-light corona calibrated data with processing level L1 from the LASCO-C2/SOHO instrument, and data from the Wind spacecraft with one-hour and one-minute time resolution on q.asi-stationary slow (v between 300-450 km/s at the Earth's orbit) the Solar Wind (SW) parameters in the absence of sporadic SW streams are examined. Within distances from the Sun's center less than R in the range of 20-30 Rs,(Rs, the solar radius), slow wind is known as the streamer belt, and at larger distances it is called the Heliospheric Plasma Sheet (HPS). It is shown that the streamer belt comprises a seq.ence of pairs of rays. In general, ray brightnesses in each pair can differ, and the magnetic field is oppositely directed in them. The neutral line of the radial magnetic field of the Sun runs along the belt between the rays of each of the *** area in which the streamer belt intersects the ecliptic plane and which lies at the central meridian, will be recorded at the earth's orbit with a time delay of 5-6 days, in the form of one or several peaks with Nmax ＞ 10 cm-3. Furthermore, the simplest density profile of the portion of the HCS has the form of two peaks of a different or identical amplitude . The such a profile is observed in cases where the angle of intersection of the streamer belt with the ecliptic plane near the Sun is sufficiently large, i.e. close to 90°. The two-ray structure of the cross-section of the streamer-belt moves from the Sun to the Earth, it retains not only the angular siz. of the peaks but also the relative density variations, and the position of the neutral line(sector boundary) in between. At the Earth's orbit the ray structure of the streamer belt provides the source for sharp (i.e. with steep fronts of a duration of a few minutes or shorter) solar wind plasma density peaks (of a duration of several hours) with maximum values Nmax ＞ 10 cm-3.

关键词： Corona Solar wind Streamer belt

Template-free Fabrication and Luminescent Characteriz.tion of Highly Uniform and Monodisperse Y_2O_2S:Sm^(3+) Hollow Submicrospheres

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2012年第7期28卷 666-672页

作者： S.q. Deng z.P. Xue Y.H. Yang q. Yang Y.L. Liu Department of Chemistry Jinan University Guangzhou 510632 China

Well dispersed and homogeneous Y2O2S：Sm3＋ hollow submicrospheres were successfully achieved by a template- free solvothermal method combining with a postcalcining process. The crystalstructure and particle morphology were investigated by the X-ray diffraction （XRD）, Fourier transform infrared （FT-IR） spectra, scanning and transmission electron microscopy （SEM and TEM）, respectively. A possible growth mechanism was proposed to reveal the formation process. Luminescence properties of the Y202S：Sm3＋ long-lasting phosphor were an- alyz.d by measuring the excitation spectra, emission spectra, afterglow decay curve and thermoluminescence curve. The excitation spectra indicated that the phosphor could be excited effectively by the ultraviolet-light emitting diode （UV-LED） or blue LED, and the emission spectra showed that the phosphor could emit red light from 600 to 650 nm.

关键词： Yttrium oxysulfide Hollow submicrosphere Luminescence Long-lasting phosphor

Effects of hysteresis of static contact angle (HSCA) and boundary slip on the hydrodynamics of water striders

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2017年第1期33卷 40-61页

作者： J. z.eng B. S. Wang W. q. chen X. Y. Han C. F. Li J. z. z.ang K. P. Yu School of Energy and Power Engineering Jiangsu UniversityZhenjiang 212013 China China Ship Scientific Research Center Wuxi 200482 China School of Astronautics Harbin Institute of TechnologyHarbin 150001 China

It is known that contact lines keep relatively still on solids until static contact angles exceed an interval of hysteresis of static contact angle (HSCA), and contact angles keep changing as contact lines relatively slide on the solid. Here, the effects of HSCA and boundary slip were first distinguished on the micro-curvature force (MCF) on the seta. Hence, the total MCF is partitioned into static and dynamic MCFs correspondingly. The static MCF was found proportional to the HSCA and related with the asymmetry of the micro-meniscus near the seta. The dynamic MCF, exerting on the relatively sliding contact line, is aroused by the boundary slip. Based on the Blake-Haynes mechanism, the dynamic MCF was proved important for water walking insects with legs slower than the minimum wave speed . As insects brush the water by laterally swinging legs backwards, setae on the front side of the leg are pulled and the ones on the back side are pushed to cooperatively propel bodies forward. If they pierce the water surface by vertically swinging legs downwards, setae on the upside of the legs are pulled, and the ones on the downside are pushed to cooperatively obtain a jumping force. Based on the dependency between the slip length and shear rate, the dynamic MCF was found correlated with the leg speed U, as , where and are determined by the dimple depth. Discrete points on this curve could give fitted relations as (Suter et al., J. Exp. Biol. 200, 2523-2538, 1997). Finally, the axial torq.e on the inclined and partially submerged seta was found determined by the surface tension, contact angle, HSCA, seta width, and tilt angle. The torq.e direction coincides with the orientation of the spiral grooves of the seta, which encourages us to surmise it is a mechanical incentive for the formation of the spiral morphology of the setae of water striders.

关键词： Seta Water strider Hysteresis of static contact angle (HSCA) Boundary slip

THE DESIGN OF AN INTEGRATED SYSTEM FOR PREDICTING AND ANALYz.NG SOLDER JOINT SHAPE AND RELIABILITY INSMT

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2000年第1期13卷 69-74页

作者： C. q. Wang X. J. z.a C. q. z.ang S. q. Yang C. z. Wang( 1)National Lab of Advanced Welding Technology, HIT, Harbin 150001, China 2)Shanghai Institute of Metallurgy, Chinese Academy of Science, Shanghai 200050, China)

Solder joint reliability is one of critical problems detemining whether Sirface Mount Technology (SMT) can be used in the prohotion of important electronic products. Optimiz.ng solder joint shape is one of effective ways to improve SMT solder joint *** this paper. based on the theorem of minimum potential energy, an energy model of 3 - D solder joint shape is established,and the forma- tion of solder joint is numerically simulated by Surface Ecolver program. On the basis of the prediction of SMT solder joint shape,the mechanical model of analyz.ng solder joint reliability is established. An elasto - plasto - creep mateial model and its mechanical constitutive eq.aton are established for SnPb solder alloy, and the stress/strain response of SMT solder joint under thermal cyclical loabing is ana- lyz.d with nonlinear 3 - D FEM. The fatigue life of solder joint is predicted according to Coffin- Manson fatigue life model. An integrated system for Predicting and analyz.ng SMT solder joint shape and reliability(PSAR) is *** system can analyz. efficiently SMT solder joint reliability with the variation of structural parameters in the joint and give the optimal structure.

关键词： SMT solder joiot relnddity solder joint shape,optimiz.tion

Localiz.d space-tim e method of fundamental solutions for three-dimensional transient diffusion problem

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2020年第5期36卷 1051-1057,I0002页

作者： L.q.u J.Lin q.-H.q.n W.chen International Center for Simulation Software in Engineering and Sciences College of Mechanics and MaterialsHohai UniversityNanjing 210098China College of Engineering and Computer Science Australian National UniversityCanberraACT 2601Australia State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China State Key Laboratory of Acoustic Institute of AcousticsChinese Academy of SciencesBeijing 100190China

A localiz.d space-time method of fundamental solutions(LSTMFS)is extended for solving three-dimensional transient diffusion problems in this *** interval segmentation in temporal direction is developed for the accurate simulation of long-time-dependent diffusion *** the LSTMFS,the whole space-time domain with nodes arranged i divided into a series of overlapping subdomains with a simple *** each subdomain,the conventional method of fundamental solutions is utiliz.d and the coefficients associated with the considered domain can be explicitly *** calculating a combined sparse matrix system,the value at any node inside the space-time domain can be *** experi-ments demonstrate that high accuracy and efficiency can be simultaneously achieved via the LSTMFS,even for the problems defined on a long-time and q.ite complex computational domain.

关键词： Localiz.d spacetime method of fundamental solutions Meshless method Long-time evolution Transient diffusion

TiS2-based saturable absorber for ultrafast fiber lasers

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Photonics Research 2018年第10期6卷 I0046-I0050页

作者： X. z.U S. chen M. z.ANG L. chen q. Wu J. z.AO q.JIANG z.z.ENG H．z.ANG School of Electronic and Information Engineering Beihang University Beijing 100191 China Department of Optoelectronics Engineering Shenzhen University Shenzhen 518060 China College of Health Science and Environmental Engineering Shenzhen Technology University Shenzhen 518118 China College of Materials Science and Engineering Shenzhen University Shenzhen 518060 China

We fabricate titanium disulfide(TiS2) using a liq.id exfoliation method and subseq.ently a TiS2-based device by optically depositing the TiS2 material onto the microfiber. This device exhibits a strong nonlinear saturable absorption property with an optical modulation depth of 8.3% at 1560 nm. With the implementation of this all-fiber TiS2-based saturable absorber, we demonstrate that both mode-locking and q.switching operation can be obtained in a turn-key all-fiber erbium-doped laser cavity. Our findings constitute the first example, to the best of our knowledge, of a TiS2-based saturable absorber for ultrashort pulse generation and highlight the great potential of such devices in two-dimensional nanomaterials-related photonics.

关键词：液体剥离方法激光器通讯技术发展现状

Electrochemical manufacturing of nanocarbons from carbon dioxide in molten alkali metal carbonate salts： roles of alkali metal cations

在线全文

学校读者我要写书评

暂无评论

Advances in Manufacturing 2016年第1期4卷 23-32页

作者： Happiness V. Ijije George z. chen Department of Chemical and Environmental Engineering Faculty of Engineering University of NottinghamNottingham NG7 2RD UK Department of Chemical and Environmental Engineering and Centre for Sustainable Energy Technologies Faculty ofScience and Engineering University of Nottingham NingboChina Ningbo 315100 People's Republic of China

One simple and fast way to manufacture a useful product from CO2 is to capture the gas by, and then carry out electrolysis in molten alkali metal carbonates. Carbon electro-deposition in molten Li2CO3-Na2CO3- KaCO3 （molar ratio： 43.5：31.5：25.0） has been widely reported in literature. However, studies in each of the individual alkali metal carbonates either have received less attention or are simply lacking in literature. Electrochem- ical studies of these molten carbonates are important to understand their underlying processes and reactions during the electrolysis. In this work, cyclic voltammograms （CVs） were recorded in each of the above-mentioned molten alkali carbonate salts using a 0.25 mm diameter Pt wire working electrode. In molten Na2CO3 and K2CO3, the main cathodic reaction was likely the formation of alkali metal, while that in Li2CO3 was carbon deposition. The results also suggest that other competing reactions such as CO and alkali metal carbide formation are possible as well in dif- ferent molten salts. On the CVs, the anodic current peaks observed are mostly associated with the oxidation of cathodic products. Flake/ring/sheet-like structures and q.asi-spherical particles were observed in the produced carbon. The morphology of the carbon contained both amorphous and graphitic structures, which varied with different electrolysis variables.

关键词： Carbon capture and utilisation Electro-deposition Cyclic voltammetry Nanocarbons Moltensalts Alkali metal carbonates

MORPHOLOGY OF AMORPHOUS SILICA DURING ALUMINUM REACTIVE PENETRATION

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2000年第4期13卷 944-948页

作者： z.ou, z. Gan, q.S. Ding, P.D. Chongq.ng Univ Chongqing China

The reduction of volume of silica glass during aluminum reactive penetration was observed experimentally. The liq.id aluminum infiltrates easily into the cavities while the released silicon is solved in the liq.id aluminum, and Al/Al2O3 composites could be obtained. The experimental results show that Al/Al2O3 composites can be transformed into Al2O3 grains by oxygen in the cavities of Al/Al2O3 composites during the longer penetration treatment. The formation of alumina is a sintering process, in which liq.id aluminum, particulate alumina and oxygen play an important role. The transformtion process has shown that there is a relationship of σAl2O3-Al2O3 2O3-Al, where σAl2O3-Al2O3 is the grain boundary energy of alumina, and σAl2O3-Al is the interface energy between aluminum and alumina. The formation temperature by aluminum reactive penetration is much lower than that by sintering.

关键词： Alumina Aluminum Metallic matrix composites Morphology Silica

SYNTHESIS AND IDENTIFICATION OF CONDUCTING POLYANILINE DOPED WITH RARE EARTH CHLORIDE

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2000年第3期13卷 872-876页

作者： Yang, C.M. z.ang, q.R. Fang, z. Central South Univ of Technology Changsha China

Polyaniline doped with rare earth chloride was synthesiz.d in organic solvent and identified by elemental analysis and infrared spectroscopy. The experimental results show that there exists both doping and complexation at the same time in the resulting product. When pH4. Moreover, polyaniline doped with rare earth chloride exhibits better thermal stability than that doped with hydrochloric acid.

关键词： Chlorine compounds Composition Conductive materials Electric conductivity Organic polymers Rare earth compounds Synthesis (chemical)